Fluid amplifiers



2 Sheets-Sheet 1 Filed May 8, 1963 FIG.2

5'0 6'0 POWER JET SUPPLY PRESSURE (PS) INVENTOR.

(POUNDS /|N CODA H.T. PAN

ATTO R N EY March 15, 1966 c. H. T. PAN 3,240,221

FLUID AMPLIFIERS Filed May 8, 1963 2 Sheets-Sheet 2 .3-- TAN e INVENTOR.CODA H.T. PAN

ATTORNEY United States Patent 01 3,240,221 FLUID AMPLIFIERS Coda H. T.Pan, Scotia, N.Y., assignor to General Electric Company, a corporationof New York Filed May 8, 1963, Ser. No. 278,887 Claims. (Cl. 13781.5)

This invention relates to fluid control devices and has particularrelation to digital and analog type fluid amplitiers.

Fluid amplifiers have the potential for wide application in variousfields due primarily to their reliability, temperature insensitivity,shock resistance, and ease of fabrication. These devices may be employedas digital and analog computing elements and also as power devices tooperate valves and the like. Fluid amplifiers may be operated aspneumatic devices employing a compressible fluid, such as gas or air, oras hydraulic devices utilizing an incompressible fluid, such as water oroil.

One of the two basic types of fluid amplifiers is of the momentumexchange type wherein a main or power fluid jet is deflected by one ormore control jets directed laterally at the power jet from oppositesides thereof. The power jet is normally directed midway between twofluid receivers, channels or apertures, and is deflected relative to thereceivers by an amount proportional to the net sideways momentum of thecontrol jets. This device is therefore often referred to as aproportional or analog device.

In the case of the analog fluid amplifier, the amount of amplificationis determined by the magnitude of angular deflection of the power jetfrom its central position, and the gain of the amplifier is a functionof the ratio of this angular deflection to the differential momentumprovided by the difference in pressure between the two control jets. Itfollows, therefore, that the greater the angular deflection of the powerjet for a fixed amount of differential momentum, the greater the gain.

It is, therefore, an object of the present invention to provide a fluidamplifier embodying improved means for the control thereof. i

It is an important object of the present invention to provide an analogtype fluid amplifier providing greater gain than has heretofore beenpossible in such analog devices.

It is another object of this invention to provide an analog fluidamplifier with enhanced gain obtained in a fluid amplifier having asimple structural geometry.

The above objects are accomplished in accordance with the principles ofthe invention by providing a cavity, chamber or recess in the side walllocated between the source of the power jet and the control jet port.The cavity or recess, at one end thereof, provides a partition or cuspformed by the juncture of the wall of the control port and the wall ofthe cavity or recess, the cavity itself being concave toward the regionof power jet flow.

With a cavity of this type on each side of the power jet flow andbetween the control jet ports and the power jet source, there isprovided effective means for enhancing the angular deflection of thepower jet with the application of a puressure differential betweencontrol jets. In the neutral or null position wherein the pressure ofthe two control jets is the same, the power jet continues along itscentrally directed path. With increased pressure from one of eitherside, the power jet is deflected toward the other side and commencesforming a vacuum in the cavity on that side. The decrease in pressure inthis cavity tends to pull the power jet even closer, thereby increasingthe angular deflection of the power jet over what would have been thecase had the cavity not been present.

In the prior art analog fluid amplifiers, the angular deflection bears adesirably linear relationship to the differof the boundary layer effecttype.

3,249,221 Patented Mar. 15, 1966 ice ential in momentum between thecontrol jets. It is an important feature of this invention, that thislinear relationship is maintained over a wide operating ran e, eventhough the gain provided in accordance :with the principles of theinvention is greatly increased over that of the prior art. Thus, inaccordance with the invention, desirable operating characteristics ofthe analog fluid amplifler of the prior art are not disturbed, whilegain is enhanced.

In the analog fluid amplifier, when the cavity is positionedsufliciently close to the path of the power jet, the application of acontrol jet differential pressure sufliciently great to deflect thepower jet by a large angle may result in providing a vacuum sufficientlygreat in the cavity to cause the jet to latch to that side. Thus, whenthe pressure differential is removed, the power jet may stay deflectedto that side, due solely to the cavity vacuum. Therefore, by a properrelationship between cavity and power jet parameters in the analog fluidamplifier, a latch- 'ing action at a particular threshold of control jetdifferential may be obtained.

The analog fluid amplifier previously mentioned is a dual polarity typedevice in that deflection from the center to one side may be considereda positive signal, while deflection to the other side may 'be considereda negative signal. In another embodiment of the invention, a singlepolarity analog fluid amplifier is provided with a control jet and acavity solely on one side. In such an ar' rangement, the cavity providesthe salutary effect of more quickly restoring the deflected signal toits central or null position upon the removal of the control jet signal.

The second of the two basic types of fluid amplifiers is In this devicepower jet deflection is effected by the side walls of an interactionchamber which are shaped in such a way that the power jet will attach toone or the other of the side walls but not to both side walls. This isbrought about by the entrainment action of the power jet wherein thepower jet tends to entrain air trapped between it and an adjacent sidewall, the entrainment becoming more effective as the power jetapproaches the adjacent side wall. This type of amplifier is basically atwo position device and for this reason is generally referred to as adigital device.

The binary fluid amplifier of the prior art therefore requires the useof one or more control jets to obtain the binary digital switchingaction.

In another embodiment digital switching is provided Without control jetsby employing a digital fluid amplifier having a power jet source and twoside recesses or cavities similar to the ones previously mentioned withrespect to the analog fluid amplifier. Thus, there is a cavity in eachof the two walls on opposite sides of the power jet and concave towardsthe power jet, but the device has no control jet ports at all. Each ofthe cavities has a vent which may be either open or closed. With bothcavity vents open, the power jet proceeds along its centrally directedpath in its null or undefiected condition. This is because the vacuumtype of action of the power jet relative to the cavities is nullified byflow out the vents from the two cavities. With one of the vents closed,however, a vacuum pump action takes place in that cavity, while thevented cavity does not have such an action. Accordingly, the vacuumbuilt up in the cavity with the closed vent tends to draw the power jettoward it and provides a new type of latching action. Digital operationis thus provided by selectively opening and closing the vents to thecavities.

In the discussion hereinafter, the term boost cavity" will be used forthe cavities, recesses, or chambers which enhance the gain of the analogfluid amplifier or provide the latching action described for the digitaldevice, in accordance with the principles of the invention.

ance with the principles of the invention;

FIGS. 2 and 3 are graphical representations of certain characteristicsof the fluid amplifier of FIG. 1;

FIG. 4 is a plan view of a variant form of the fluid amplifier of FIG.1; and

FIG. 5 is a diagrammatic view in perspective illustrating a digitalfluid amplifier embodiment constructed according to the invention.

Referring now to the drawings in greater detail, there is illustrated inFIG. 1 an embodiment of the invention,

given by way of example, in the form of an analog type fluid amplifierrepresented generally by the numeral 10. The device is diagrammaticallyshown in FIG. 1 as including a plate 11 formed of suitable material,such as metal, plastic or the like, which is slotted in a specialconfiguration to provide passages for fluid. The various slots in theplate 11 may be formed in any suitable manner and may extend entirelythrough the plate or may be of lesser depth as desired. In theillustrated embodiment,

the slots in the plate 11 are shown extending only partiallytherethrough.

The plate includes a main opening 12 into which extends a conduit orpassage 13 which carries pressurized fluid into the opening 12, it beingunderstood that suitable enclosure such as a covering plate 9 ispositioned on top side of plate 11 to confine fluid to the various slotsof the plate 11.

The fluid utilized in the control device may assume a variety of forms.For example, the fluid may constitute a compressible fluid, such as air,to provide a pneumatic device. As a further example, the fluid may beincompressible, such as oil or water, to provide a hydraulic device.

Communicating with the opening 12 is a restricted slot 14 constituting apower nozzle from which issues a jet ,of fluid emanating from theconduit 13. At a distance from the juncture of nozzle 14 and opening 12,and on opposite sides of the centerline extension of nozzle 14, arelocated a pair of slots 15 and 16 which may be designated control slotsand into which extend conduits or passages 17 and 18 for introducingpressurized fluid into the control slots. The conduits 17 and 18 may besupplied with pressurized fluid in any suitable manner, such as from thesame source which supplies the conduit 13 or from independent sources asdesired. As is understood in the art, pressurized fluid in the controlslots 15 and 16 cooperate upon a pressure difierential basis to deflectthe jet issuing from nozzle 14.

In the illustrated embodiment, plate 11 is formed with two elongateddiverging fluid receiving passages 22 and 24, which selectively receivefluid of the power jet depending upon the direction and magnitude ofangular deflection of the power jet. The passages or channels 22 and 24are separated by a third channel 23, whose centerline is a co-linearextension of that of nozzle 14. The downstream end of receiver 23 may bevented to the atmosphere or may be employed to drive some useful load. Amajor portion of the power jet flow from nozzle 14 passes into andthrough receiver 23 when there is a null pressure diiferential betweenthe control jets from slots 15 and 16. When the pressure of the controljet from either of the two slots 15 or 16 is greater than that of theother, the power jet from nozzle 14 is deflected in the direction of theside wherein the control jet pressure is lower. The angular deflection 6of the power jet, with 0 being measured from the centerline of slot 14to the centerline of the deflected power jet, determines what portion ofthe power jet enters receiver 22 or 24 and what portion enters the nullreceiver 23. When 0 is at its magnitude 0 there is alignment of thecenterline of the jet with the centerline of receiver 22 or 24, withlittle of the power jet exiting through the null receiver 23. Thus, theportion of the power jet entering receiver 22 or 24 is a continuouslyvariable analog signal proportional to the angle 0, and thereforedirectly proportional to the control jet pressure diiferential.

The geometry and operating characteristics of the fluid amplifier ofFIG. 1, as thus far described, is that of a conventional analog fluidamplifier. However, the amplifier of FIG. 1 is not conventional in thegeometry of the walls between nozzle 14 and control slots 15 and 16.Thus, directly between the constricted throat 14 and control port 15,and forming the wall boundary therebetween, is a boost cavity 31, orrecess, having an arc-uate configuration, which may be substantiallysemicircular, and oriented concave toward the path of the power jet.Cavity 31 formed in this manner is defined in part by a wall section 33which constitutes a partition, septum or cusp formed between the wallsof cavity 31 and control port 15. Thus, the control jet issuing tion,septum or cusp formed between the walls of cavity 31, or putting itanother way, the cavity 31 is shielded from the effect of the controljet by septum 33. On the other side of the power jet path the wallbetween control port 16 and throat 14 is similarly formed as a cavity orrecess 35 with a similar septum 37. The ends 43 and 47 of the septa 33and 37 are spaced from each other and from the power jet boundarysufliciently so that the pressure in boost cavities 31 and 35 isapproximately the same as the fluid pressure at the exit of control jetports 15 and 16 when the power jet is in its null position and receivedmainly by null receiver 23.

In operation, when the control jet pressure on one side is greater thanthat on the other, for example when the pressure from control port 15 isthe greater, then the clearance between the boundary of the power jet onthe right and cavity 35 is reduced. This results in a partial vacuumbeing created in boost cavity 35, which in turn results in a largereffective control pressure differential, and therefore results in alarger deflection angle 0 than would be the case had the boost cavity 35not been there. Conversely, if the pressure from port 16 had been thegreater, deflection would have been to the left toward boost cavity 31,with a similar type of enhanced action in the opposite angulardirection.

To more fully appreciate the gain enhancement provided by the boostcavities 31 and 35 in accordance with the principles of the invention,there are presented in FIG. 2 curves 48 and 49 which represent functionsof the angular deflection for prior art fluid amplifiers and a fluidamplifier of the invention, respectively, at various power jet supplypressures. The ordinate of FIG. 2 is position gain, which is a functionof the power jet angular deflection normalized with respect to thevariables of control pressure differential, and control port and powernozzle dimensions. More specifically, the ordinate is equal to:

AtanB the prior art analog fluid amplifiers. All pressures mentioned aregauge pressures, with the gauge reference being the pressure in theinteraction chamber.

In FIG. 3, are shown curves 51 and 52 which represent the angulardeflection obtained in a fluid amplifier in accordance with theinvention, as a function of control jet pressure differential, and morespecifically, as a func- Curves 5-1 and 52 are for power jets havingsupply pressure of 15 and 44 pounds per square inch, respectively. Itmay be noted that the relationship between angular deflection andcontrol jet differential pressure is maintained substantially linearover a wide operating range.

In the construction of the fluid amplifier of FIG. 1, it is believedthat certain relationships in the geometry of the amplifier shouldpreferably be provided. Thus, for example, the distance of receivers 22,23 and 24 from the power jet nozzle 14 is preferably five to eight timesthe width d of the power jet nozzle. The spacing of receivers 22 and 24from the center line may be selected dependent upon whether pressurerecovery or power recovery is of more importance. It pressure recoveryis of main interest, then the idealized point location of the receiverfrom the power jet nozzle center line should be 0.6 where y is thelateral distance from the jet axis to the point where the velocity ofthe power jet is half that of the velocity of the power jet at itscenter line. Where power recovery is of more interest, optimum powerrecovery is obtained with a receiver having a width equal to 2yFurthermore, with two receivers of this width spaced with each adistance y from the center line, the resulting configuration providesthe greatest power gain (but such an arrangement precludes a centerreceiver).

It may be noted from the curves of FIG. 2 that position gain is afunction of power jet supply pressure, and that gain decreases with anincrease in supply pressure. This is due in part to the fact thatincreased power jet supply pressure results in the pivot point 26 (FIG.1), which effectively defines the point at which angular deflection 6commences, moving downstream. The greater the supply pressure, thegreater the distance downstream that pivot point 26 is moved, andangular deflection decreases as a consequence.

In the analog fluid amplifier of FIG. 1, deflection of the power jet tothe angle 9 which provides a complete correspondence between the powerjet and one of the receivers 22 or 24, results in bringing the boundaryof the power jet in intimate association with the boost cavity cusp.Accordingly, the vacuum within the boost cavity at that angulardeflection is ordinarily sufliciently great such that when the pressurediflerential between the control jets is removed, the power jet remainsfixed in its 9 deflected position. Accordingly, the amplifier of FIG. 1not only provides analog amplification but also provides a latchingfunction in that when the control jet pressure differential reaches aparticular threshold level, the jet remains latched to that side.

Referring to FIG. 4, there is shown a plan view of an analog type fluidamplifier of the same type as that of FIG. 1, except that solely oneboost cavity 61 and control jet port 62 appear, and only one receiver 64other than the null receiver 65 is provided. In the embodiment of FIG.4, deflection is by a control jet from port 62 on the same side as theboost cavity 61 and accordingly, deflection of the power jet is awayfrom boost cavity 61. Removal of the control jet pressure results in thepower jet resuming its null condition and exiting through receiver 65.Due to the boost cavity 61 on the side toward which the deflected powerjet returns, some vacuum is created in boost cavity 61 as the power jetis in the process of returning from its deflected position.

'6 This tends to increase the speed of return and tends to snap the jetback to the null position.

In the embodiment of FIG. 5, a digital fluid amplifier is represented inaccordance with the principles of the invention. It may be noted thatthis digital device has a structure which varies from that of the analogdevice of FIGS. 1 and 4 in several respects. Thus, there are no controljet ports at all. The boost cavities 71 and 72 which are locatedadjacent the end of power jet nozzle 74 are substantially similar tothose of FIG. 1. However, each of the boost cavities is veritable by avent pipe as shown. Fluid flow through vent pipe 75 for cavity 71 iscontrolled by valve 76 which is preferably of the type that is normallyfully open or closed and may be rapidly switched from one state to theother. A similar valve 77 is provided in the vent pipe 78 for the otherboost cavity 72.

In operation, closing of valve 76 while leaving valve 77 open results invacuum pump action building up in cavity '71, to thereby cause the powerjet .to deflect toward boost cavity 71. This is a positive feedback typeof action such that the deflection continues until the boundary layer ofthe power jet is in contact with the cusp 79 of boost cavity 71.Accordingly, the power jet remains latched to that side. This providesone of the two binary switching positions for this binary type fluidamplifier. If it is desired to switch the power jet to the opposite sideand therefore to the second of the binary positions, valve 76 for cavity71 is opened while simultaneously, valve 77 for boost cavity 72 isclosed. The conditions are thereby reversed. The vacuum that had beencreated in boost cavity 71 is broken, and pressure builds up, whilevacuum pump action commences in boost cavity 72 because of the closedvent 77. In this way, binary switching action is obtainable andflip-flop action is provided without the need for control jet ports andcontrol jet supplies. Simple electromechanical switching means may beemployed if desired for automatically actuating the vent valves forproviding the desired switching action.

While the principles of the invention have now been made clear inillustrative embodiments, there will be immediately obvious .to thoseskilled in the art many modifications in structure, arrangement,proportions, the elements, materials, and components, used in thepractice of the invention, and otherwise, which are particularly adaptedfor specific environments and operating requirements, without departingfrom those principles. The appended claims are therefore intended tocover and embrace any such modifications, within the limits only of thetrue spirit and scope of the invention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. A fluid amplifier comprising: a power jet nozzle for projecting afluid power jet having a boundary layer; a plurality of fluid receivingmeans positioned downstream from said power jet nozzle; a control jetport adjacent said nozzle for directing a first fluid control jet atsaid power jet; and a concave recess in the wall formed between the wallforming said nozzle and the Wall forming said port, the terminatingpoints of said concave recess being positioned adjacent the boundarylayer of said fluid power jet whereby a low pressure is formed in saidconcave recess to exert a force on said jet.

2. A fluid amplifier as recited in claim 1 wherein said recess isconcave toward the path of said power jet.

3. A fluid amplifier as recited in claim 2 wherein the boundary formingsaid recess is arcuate in shape.

4. A fluid amplifier as recited in claim 2 wherein said concave recesshas an end wall portion forming a cusp with an end wall portion of saidcontrol port.

5. A fluid amplifier as recited in claim 4 wherein said cusp is spaced adistance from the boundary layer of said power jet for all power jetsupply pressures in the operating range of said fluid amplifier.

6. A fluid amplifier as recited in claim 1 including a 7 second controljet port on the opposite side of said power jet nozzle from said firstcontrol jet port; and a second concave recess in a wall formed betweensaid nozzle and said second control jet port.

7. A fluid amplifier as recited in claim 6 wherein said second concaverecess is concave toward the path of said power jet.

8. A fluid amplifier comprising: a power jet nozzle for projecting afluid power jet having a boundary layer; a plurality of fluid receiverspositioned downstream from said power jet nozzle; a control jet portadjacent said nozzle for directing a first fluid control jet at saidpower jet; and means comprising a cavity disposed between said nozzleand said port, said cavity having an opening adjacent to a portion ofthe boundary layer of said power jet for decreasing fluid pressure in aregion contiguous to said portion of said boundary layer when said powerjet is deflected from a given angular orientation.

9. A fluid amplifier comprising: a jet nozzle for projecting a jet offluid along a path, said jet of fluid having a boundary layer; aplurality of fluid receiving means positioned downstream from said jetnozzle; and control means positioned adjacent said path and saidboundary layer for varying the direction of said path, said controlmeans comprising a control jet port adjacent said nozzle for directing afluid control jet at said power jet and means defining a cavity havingan opening adjacent said boundary layer, said cavity being positionedbetween said jet nozzle and said control jet port, said cavityproducing, in response to the passage of said jet of fluid adjacent tosaid opening, a region of reduced fluid pressure contiguous to saidboundary layer and including said cavity.

10. A fluid amplifier comprising: a jet nozzle for the projection of ajet of fluid along a path, said jet of fluid having a boundary layer; aplurality of fluid receiving means positioned downstream from said jetnozzle; and control means for changing the direction of said path, saidcontrol means comprising a control jet port adjacent said nozzle fordirecting a fluid control jet at said power jet and means defining atleast one concave recess disposed adjacent the boundary layer of saidjet of fluid for producing a reduction in fluid pressure in a regioncontiguous to said boundary layer and including said recess in responseto the projection of said jet of fluid, said recess being positionedbetween said jet nozzle and said control jet p-ort.

References Cited by the Examiner UNITED STATES PATENTS 3,080,886 3/1963Severson 13781.5 3,122,062 2/1964 Spivak et a1. 13781.5 3,144,037 8/1964Cargill et al. 137-815 3,148,691 9/1964 Greenblott l378l.5

M. CARY NELSON, Primary Examiner.

LAVERNE D. GEIGER, Examiner.

1. A FLUID AMPLIFIER COMPRISING: A POWER JET NOZZLE FOR PROJECTING AFLUID POWER JET HAVING A BOUNDARY LAYER; A PLURALITY OF FLUID RECEIVINGMEANS POSITIONED DOWNSTREAM FROM SAID POWER JET NOZZLE; A CONTROL JETPORT ADJACENT SAID NOZZLE FOR DIRECTING A FIRST FLUID CONTROL JET ATSAID POWER JET; AND A CONCAVE RECESS IN THE WALL FORMED BETWEEN THE WALLFORMING SAID NOZZLE AND THE WALL FORMING SAID PORT, THE TERMINATINGPOINTS OF SAID CONCAVE RECESS BEING POSITIONED ADJACENT THE BOUNDARYLAYER OF SAID FLUID POWER JET WHEREBY A LOW PRESSURE IS FORMED IN SAIDCONCAVE RECESS TO EXERT A FORCE ON SAID JET.